I sense a bit of arrogance and perhaps snobbishness when folks claim that top end gear is provably better than mid range.
I will grant that the low end stuff can be terrible by most anybodys standards.
But can anybody *prove* that high end gear is better and not merely different?
I think you're missing the point...
If you've heard really good preamplifiers with an excellent S/N ratio and everything else that goes with them then when you then hear preamps with a less impressive performance you are far more conscious of their shortcomings compared to the 'better-specced' pres. Such is life.
An example from today... Yesterday I shot some video using a radio mic system. Not expensive but uber-portable and easy to use. As far as I was concerned it had some significant failings: poor noise floor and constant micro dropouts. All my other radio mic gear comes from higher up the food-chain. I was moaning to my wife about this earlier today and she said, "But will anyone but you notice?" Of course the answer was "Probably not, but I do!"
When you're accustomed to using top-quality gear you're more likely to perceive issues and inadequacies with more modest gear. Does that mean it's no good? Of course not - unless it's performance is not fit for purpose. Most of those here who are accustomed to using good gear are too mature to rubbish more modest stuff, but it doesn't stop them buying top-quality gear if they can afford it.